U.S. Pat. No. 4,450,037 in particular discloses a device for moistening and closing envelopes comprising, downstream of a pair of drive rollers, a separator for separating the flap from the body of the envelope, a moistener for moistening the flap thus moved apart and, disposed between this pair of rollers and the separator, a manually mobile deflector which, depending on its position of selection, allows the passage of closed envelopes not having to be moistened or the passage of envelopes with folded down, non-stuck flaps.
However, apart from the fact that this device does not allow the passage of nested envelopes, it presents the major drawback of requiring a prior sorting of the envelopes unless the position of the mobile deflector is constantly modified, which prevents any high-speed functioning.
It is therefore an object of the present invention to propose a universal moistening device, i.e. one capable of moistening nested envelopes as well as envelopes with folded down flaps but also of allowing the passage, without moistening, of closed envelopes as well as any other document having to be printed thereafter. Another object of the invention is to allow a perfect moistening whatever the thickness of the envelopes handled. Another object of the invention is to produce such a device in simple and inexpensive manner. Yet another object of the invention is to integrate this device in a conventional high-speed feed structure.